diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 748702eb89..d2ed052b06 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -3012,9 +3012,11 @@ list {
   > row.expander { padding: 0px; }
   > row.expander .row-header { padding: 2px; }
 
+  &.horizontal row.separator:not(:first-child),
   &.separators.horizontal row:not(:first-child) {
     border-left: 1px solid $borders_color;
   }
+  &:not(.horizontal) row.separator:not(:first-child),
   &.separators:not(.horizontal) row:not(:first-child) {
     border-top: 1px solid $borders_color;
   }